WAEC Physics 2020 Objective — Question 11
Question 11 of 50 from the West African Examinations Council (WAEC) Physics 2020 Objective paper, with the correct answer and a full explanation.
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Which of the following statements explains why hot soapy water is more effective in cleaning oil-stained dishes? A. The oil on the dishes repels the soap. B. Soap and heat decrease the surface tension of water. C. Hot water increases the surface tension of oil. D. Soap increases the surface tension of oil and water.
- A. The oil on the dishes repels the soap
- B. Soap and heat decrease the surface tension of waterCorrect
- C. Hot water increases the surface tension of oil
- D. Soap increases the surface tension of oil and water
Explanation
Hot soapy water lowers the net force of attraction among molecules and hence decreases surface tension, allowing it to more effectively clean oil-stained dishes.
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